Finite element analysis of rotary blanking: Effects of punch geometries on cutting area and stress distribution

It is essential to develop efficient and cost-effective production methods to achieve or maintain international competitiveness. An innovative production method, such as rotary blanking, enables manufacturers to both reduce expenses and economize production time. However, there are not enough numerical analyses for this process. In this paper, numerical simulations of rotary blanking were performed. After comparing the cutting planes generated by conventional and rotary blanking experimental tests, the cutting areas of two punch geometries were analyzed. The influence of punch geometry on part quality was then investigated through simulations. The procedure for die stress analysis was established and stress distributions of the worksheet and the tools were analyzed.     

Measurement of soot oxidation with No<Subscript>2</Subscript>-O<Subscript>2</Subscript>-H<Subscript>2</Subscript>O in a flow reactor simulating diesel engine DPF

Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration. Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO₂-O₂-H₂O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of NO₂-O₂ oxidation, which was 60±3 kJ/mol. When NO₂ exists with O₂ and H₂O, the reaction rate increases in proportion to NO₂. It increases nonlinearly with O₂ or H₂O concentration when the other two oxidants are fixed.     

Impedance-based and circuit-parameter-based battery models for HEV power systems

The relationship between voltage and current inside a battery, or the impedance, plays an important role in the simulation and design of hybrid electric vehicle (HEV) power systems. This paper proposes a new approach employing the Bode plot for evaluation of equivalent circuit parameters for a lithium polymer battery (LiPB) for HEV application. The main concept of the proposed circuit-parameter-based model approach is the application of a transfer function used to process the frequency response of the battery for calculation of accurate circuit parameters. Additionally, the Bode plot is also applied to derive the impedance-based model directly from frequency response measurements for short time simulations and practical use in the HEV. Two methods for battery modeling are proposed and verified experimentally with the voltage-current profile of a conventional HEV using the battery measured in this paper. The results show that the proposed circuit-parameter-based technique provides a satisfactory battery equivalent circuit model.     

Development of a hydraulic limited slip differential system using a pressure generator

The limited slip differential (LSD) is a device that enables the driving force to be transmitted from one slipping wheel to the other by temporarily restraining the differential function when unwanted slipping occurs on muddy or icy roads. Many types of LSD have been developed, such as mechanical lock, disk clutch, viscous coupling, torsen and multiple clutch. This study designed a new type of hydraulic LSD using a pressure generator base on a trochoid gear pump and evaluated the performance of the new design.     

Numerical modeling of hollow-cone fuel atomization,vaporization and wall impingement processes under high ambient temperatures

In the following paper, a numerical study of the atomization, vaporization and wall impingement processes of hollow-cone fuel spray from high-pressure swirl injectors under various ambient temperature conditions was carried out. Also, the availability of applied models and the effect of ambient temperature on spray characteristics is discussed. The Linearized Instability Sheet Atomization (LISA) model combined with the Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model, the improved Abramzon model and the Gosman model are used to calculate the atomization, vaporization and wall impingement processes of hollow-cone fuel spray, respectively. Spray models are implemented with the modified KIVA code. The calculation results of the spray characteristics under two ambient temperatures, including spray tip penetration, spray structure and radial distance after spray-wall impingement are compared to the experimental results obtained by the Laser Induced Exciplex Fluorescence (LIEF) technique. The droplet size distribution, ambient gas velocity field, vapor phase distribution and fuel film mass generated by spray-wall impingement, measurements which are generally difficult to obtain by experimental methods, are also calculated and discussed. Quantitative discussions on the effect of the ambient temperature on the spray development process are conducted. It is shown that the applied models are applicable even in the high ambient temperature condition.     

Development of fuel cell hybrid powertrain research platform based on dynamic testbed

An experimental research platform based on a dynamic testbed is developed and applied for fuel cell hybrid powertrain integration and control. A driver brake model is added to the dynamic testbed to simulate the braking process of an electric vehicle. Sub-systems of the fuel cell hybrid powertrain are tested, and characteristic parameters are obtained. A simulation platform is constructed in LabVIEW environment, and its validity is verified by dynamic test results. A real time control system is developed with an embedded PC for the function of rapid control prototyping. Using this platform, fuel cell battery hybrid and fuel cell supercapacitor hybrid configurations are investigated. This platform provides a powerful tool for fuel cell powertrain research and development.     

Investigation of influential factors of a brake corner system to reduce brake torque variation

This paper investigates the brake corner system to reduce brake torque variation in the brake judder problem. A numerical model for determining brake torque variation was constructed using the multi-body dynamics model. Using this model, the brake torque variation for a given disc thickness variation was obtained in the time domain. The multi-body dynamics model was verified by a dynamometer test via the comparison of brake torque variation and load distribution patterns of the pad. To reduce the simulation time and cost required to determine factors that influence the reduction in brake torque variation, a simple mathematical model was constructed and used to determine both the brake torque variation and influential factors. The multi-body dynamics model and dynamometer test were modified on the basis of the results of the simple mathematical model and deformed shape of the multi-body dynamics model. These influential factors were verified to reduce the brake torque variation.     

Effects of coolant channels on large-scale Polymer Electrolyte Fuel Cells (PEFCS)

Fully coupled simulations of two-phase transport in Polymer Electrolyte Fuel Cells (PEFCs) and heat transfer in coolant channels are performed in order to investigate the effects of cooling channel configuration on the distributions of temperature and water within PEFCs. When a practical coolant flow rate is applied to large-scale cells for automotive applications, a significant coolant temperature rise is expected from the coolant inlet to the outlet, particularly under high current density operations, creating a significant cell temperature gradient along the flow direction as well. Consequently, a two-phase water profile resulting from evaporation-condensation processes inside PEFCs is also strongly influenced by the cell temperature gradient from the hot coolant inlet toward the cold coolant outlet regions, demonstrating that both temperature and liquid saturation strongly depend on the thermal gradient along the coolant flow path.     

Analysis and optimization of air suspension system with independent height and stiffness tuning

Suspensions play a crucial role in vehicle comfort and handling. Different types of suspensions have been proposed to address essential comfort and handling requirements of vehicles. The conventional air suspension systems use a single flexible rubber airbag to transfer the chassis load to the wheels. In this type of air suspensions, the chassis height can be controlled by further inflating the airbag; however, the suspension stiffness is not controllable, and it depends on the airbag volume and chassis load. A recent development in a new air suspension includes two air chambers (rubber airbags), allowing independent ride height and stiffness tuning. In this air suspension system, stiffness and ride height of the vehicle can be simultaneously altered for different driving conditions by controlling the air pressure in the two air chambers. This allows the vehicle’s natural frequency and height to be adjusted according to the load and road conditions. This article discusses optimization of an air suspension design with ride height and stiffness tuning. An analytical formulation is developed to yield the optimum design of the new air suspension system. Experimental results verify the mathematical modeling and show the advantages of the new air suspension system.     

Numerical study to evaluate the characteristics Of HVAC-related Parameters to reduce CO<Subscript>2</Subscript> concentrations in cars

Today, as people are spending increasing amounts of time in their cars, they have come to recognize that the car should function as a “residential” space. An eco-friendly indoor environment that provides comfort in terms of visual, tactile, and auditory senses is needed for the driver and the passengers. The quality of the car’s indoor environment was evaluated on various factors, such as indoor thermal comfort, indoor air quality, smell, and noise. For the indoor air quality, the typical pollutants that degrade the air quality are CO₂, volatile organic compounds, and exhaust gases. Especially, CO₂ has a direct relationship with drowsy driving which leads to traffic accidents. There have been many experimental and analytical studies to reduce the level of CO₂ in a short time, but analyses of parameters that affect indoor CO₂ concentration are insufficient and comprehensive standards for evaluating the car indoor CO₂ concentration do not yet exist. In this study, several parameters were selected that can influence the reduction rate of CO₂ concentration, and a series of computational analyses were conducted to study the results of these parameters in CO₂ reduction. Based on this study, a prediction equation for CO₂ concentration was derived. For this, a general full factorial design was used to evaluate the CO₂ reduction characteristic based on various parameters (ventilation mode, boarding condition, vent angle, mass flow rate, and operation mode), and then their effects were analyzed to obtain an evaluation database of indoor air quality. From that, a prediction equation was derived to estimate the indoor air quality, enabling us to evaluate the CO₂ concentration quickly that actually influences the human body without carrying out time-consuming CFD analyses for CO₂ concentration. This study will be useful in designing HVAC systems and establishing the control logic for effective improvement of the car’s indoor air quality in the future.